Critical examination of isolation system design paradigms for a coupled powertrain and frame: Partial torque roll axis decoupling methods given practical constraints

The torque roll axis motion decoupling concept is analytically and computationally studied in a realistic coupled powertrain and frame system using discrete, proportionally damped linear models. Recently, Hu and Singh (2012 1]) (Journal of Sound and Vibration 331 (2012) 1498–1518) proposed new paradigms to fully decouple such a system. However, critical examination shows that the derivation does not always lead to a physically realizable system, as each powertrain mount is not referenced to a single location. This deficiency is overcome by deriving mount compatibility conditions to ensure realistic mount positions which are incorporated into proposed decoupling conditions. It is mathematically shown that full decoupling is not possible for a practical system, and therefore partial decoupling paradigms are pursued. Powertrain mount design using only the decoupled powertrain achieves better decoupling than minimizing conditions for the coupled system using a total least squares method. Further decoupling is obtained through frame isolation design using a decoupled frame model such that the torque roll mode is dominant over the frequency range considered. Other methods for limiting frame coupling are also briefly discussed.